This invention relates to station controller units and, in particular, to station controller units used with centrex exchanges for permitting the exchanges to more easily accommodate a multi-station pick-up capability.
U.S. Pat. No. 4,885,769, assigned to the same assignee hereof, describes a telephone system in which a number of station controller units each associated with a number of telephone stations, are interposed between their respective telephone stations and a centrex exchange. Each controller unit communicates with the cable pairs connected to its associated telephone stations. These cable pairs, in turn, are connected to specific equipment ports of the centrex exchange.
As described in the '769 patent, each station controller unit is adapted to couple control, voice and data information between its associated telephone stations and the centrex exchange. Where the telephone stations are digital telephone stations operating on the Integrated Systems Digital Network (ISDN) standard, this coupling is through a control channel, the so-called "D channel" and through two other channels, the so-called "B channels", one for voice signals and the other for data signals. This communication furthermore is in packet form with information packets being continuously passed between the controller and the telephone stations.
The station controller units of the '769 patent are further adapted to provide signals for controlling the lamps of the telephone stations of the system which are arranged in so-called multi-station pick-up groups. Each multi-station pick-up group defines a set of stations each of which can pick-up for every other station in the group. To permit this pick-up capability, each station of a multi-station pick-up group is provided with lamps corresponding to the other stations of the group to indicate the status of these other stations.
As described in the '769 patent, each station controller unit monitors the status (off-hook, ringing, etc.) of each associated telephone station via the respective D channel and in response to a status change places a status control signal on a local area network which connects all the station controller units. Each station controller unit upon receipt of a status control signal on the local area network processes the status control signal through a map which correlates each telephone station served by the controller with the other stations in its pick-up group.
If a status control signal is in a pick-up group of one or more of the stations served by a controller, the controller then provides signals over its D channels to the appropriate telephone stations. These stations, in turn, change the conditions of their appropriate lamps to reflect the changed status.
The station controller units and the local area network in the '769 patent thus permit the centrex exchange to have a multi-station pick-up capability, while relieving the centrex of having to provide the lamp status control signals for the telephone stations. Moreover, connection of a picking-up telephone is still carried out by the centrex exchange itself. This occurs via a pick-up signal actuated by a pick-up key on the picking-up telephone station.
The pick-up signal is conveyed by the appropriate station controller to the centrex exchange and processed by the exchange via a multi-station pick-up group map. The latter allows the exchange to correlate a telephone station being rung with pick-up signals from other stations in the rung telephone station's pick-up group. Upon receipt of a pick-up signal, the centrex establishes a virtual connection to the picking-up telephone station so that the call can be answered.
The station controller units of the '769 patent, therefore, need no switching capability and thus can be of simpler construction. Moreover, with these controllers, telephone stations served by different controllers can be in the same pick-up group.
While the station controller units and system of the '769 patent are thus advantageous, there is also a desire in systems of this type to be able to move a telephone station from one cable pair to another in the system without changing the directory number of the station and class of service being provided to the station. This permits a subscriber to move from one location to another in the system without affecting the subscriber's telephone service.
In many centrex systems, this is accomplished by a change order being written which updates the cable pair information for the telephone station being moved. This cable information includes the directory number (i.e., identity) of the telephone station being moved and the identity of the old and new cable pairs.
The written change order is then conveyed to a recent change maintenance and administrative center where it is electrically transmitted to the centrex exchange through its so-called "recent change port". Cable information received at this port is used by the exchange to establish and update a correlation or translation table which is maintained by the centrex exchange to correlate the equipment ports of the exchange with the associated cable pairs and with the directory numbers (identities) of the telephone stations served by the cable pairs.
When cable information is received by the centrex exchange indicating a directory number (i.e., identity) of a telephone station and the old and new cable pairs, the correlation table is appropriately changed, deleting the directory number from the old cable pair entry and entering it onto the new cable entry. The centrex now correlates the directory number and its telephone station with the new cable pair and, in particular, with the centrex equipment port connected to that cable pair.
Their are some centrex changes (e.g., the No. 5 ESS) in which the aforesaid change in cable pair can be processed automatically by the centrex exchange during initial connection of the telephone station to the new cable pair. Additionally, station controller units which have a switching capability can also accomplish this via their switching circuitry.
However, many centrex exchanges do not have this automatic capability and have to use the written change order procedure discussed above. Also, station controller units using switching circuitry are not as desirable as units, such as the '769 controller unit, which do not require such circuitry. It, therefore, would be beneficial to accomplish automatic processing of telephone station moves to new cable pairs with a station controller unit that does not require the use of switching equipment.
It is, therefore, a primary object of the present invention to provide a station controller unit not having a switching network for use in providing a multi-station pick-up capability to a centrex exchange and which also permits the automatic monitoring of the movement of a telephone station from one cable pair to another.
It is a further object of the present invention to adapt the station controller unit of the '769 patent to achieve the aforementioned objective.